ASVAB Mechanical Comprehension Practice Test 876579 Results

Your Results Global Average
Questions 5 5
Correct 0 3.22
Score 0% 64%

Review

1

If the handles of a wheelbarrow are 3 ft. from the wheel axle, what force must you exert to lift the handles if it's carrying a 270 lb. load concentrated at a point 0.5 ft. from the axle?

56% Answer Correctly

45 lbs

0.83 lbs

810 lbs

90 lbs
Solution

This problem describes a second-class lever and, for a second class lever, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance: Fede = Frdr. Plugging in the variables from this problem yields:

Fe x 3 ft. = 270 lbs x 0.5 ft
Fe = 135 ft-lb. / 3 ft 
Fe = 45 lbs

2 A = 5 ft., the green box weighs 15 lbs., and the blue box weighs 35 lbs. What does distance B need to be for this lever to balance?
65% Answer Correctly
8.57 ft.
4.29 ft.
2.14 ft.
7 ft.
Solution
In order for this lever to balance, the torque acting on side A must equal the torque acting on side B. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

fAdA = fBdB

For this problem, the equation becomes:

15 lbs. x 5 ft. = 35 lbs. x dB

dB = \( \frac{15 \times 5 ft⋅lb}{35 lbs.} \) = \( \frac{75 ft⋅lb}{35 lbs.} \) = 2.14 ft.

3

An inclined plane increases ___________ to reduce ____________.

58% Answer Correctly

force, distance

force, power

distance, power

distance, force
Solution

An inclined plane is a simple machine that reduces the force needed to raise an object to a certain height. Work equals force x distance and, by increasing the distance that the object travels, an inclined plane reduces the force necessary to raise it to a particular height. In this case, the mechanical advantage is to make the task easier. An example of an inclined plane is a ramp.

4 If you lift a 43 lbs. rock 8 ft. from the ground, how much work have you done?
70% Answer Correctly
0 ft⋅lb
35 ft⋅lb
344 ft⋅lb
51 ft⋅lb
Solution
Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 43 \times 8 \)
\( W = 344 \)
5 If the green arrow in this diagram represents 440 ft⋅lb of work, how far will the box move if it weighs 220 pounds?
72% Answer Correctly
55 ft.
440 ft.
2 ft.
0 ft.
Solution
The Law of Work states that the work put into a machine is equal to the work received from the machine under ideal conditions. In equation form, that's:

Win = Wout
Feffort x deffort = Fresistance x dresistance

In this problem, the effort work is 440 ft⋅lb and the resistance force is 220 lbs. and we need to calculate the resistance distance:

Win = Fresistance x dresistance
440 ft⋅lb = 220 lbs. x dresistance
dresistance = \( \frac{440ft⋅lb}{220 lbs.} \) = 2 ft.